Influence of increasing temperature and salinity on herbicide toxicity in estuarine phytoplankton

Abstract

Ecological risk assessments are, in part, based on results of toxicity tests conducted under standard exposure conditions. Global climate change will have a wide range of effects on estuarine habitats, including potentially increasing water temperature and salinity, which may alter the risk assessment of estuarine pollutants. We examined the effects of increasing temperature and salinity on the toxicity of common herbicides (irgarol, diuron, atrazine, and ametryn) to the phytoplankton species Dunaliella tertiolecta. Static 96-h algal bioassays were conducted for each herbicide under four exposure scenarios: standard temperature and salinity (25°C, 20 ppt), standard temperature and elevated salinity (25°C, 40 ppt), elevated temperature and standard salinity (35°C, 20 ppt), and elevated temperature and elevated salinity (35°C, 40 ppt). The endpoints assessed were algal cell density at 96 h, growth rate, chlorophyll a content, lipid content, and starch content. Increasing exposure temperature reduced growth rate and 96-h cell density but increased the cellular chlorophyll and lipid concentrations of the control algae. Exposure condition did not alter starch content of control algae. Herbicides were found to decrease growth rate, 96 h cell density, and cellular chlorophyll and lipid concentrations, while starch concentrations increased with herbicide exposure. Herbicide effects under standard test conditions were then compared with those observed under elevated temperature and salinity. Herbicide effects on growth rate, cell density, and starch content were more pronounced under elevated salinity and temperature conditions. To encompass the natural variability in estuarine temperature and salinity, and to account for future changes in climate, toxicity tests should be conducted under a wider range of environmental conditions.

Climate change–contaminant interactions in marine food webs: Toward a conceptual framework

“…Of particular consideration is also the impact of climate change on contaminant toxicity. For instance, under climate change effects on temperature, salinity, and pH , empirical studies on toxicity testing of pesticides in phytoplankton and invertebrates have shown increased toxicity by 4–5 times at higher temperatures and salinities relative to standard conditions (see DeLorenzo, Danese & Baird, ; DeLorenzo, Wallace, Danese & Baird, ). Conversely, pollutant‐induced climate change susceptibility conspires against the adaptability of organisms and food webs to make levels of biological organization more vulnerable to climate change risk and impacts, thus reducing ecosystem resiliency.…”

A bentazone-resistant mutant of cyanobacterium, Synechococcus elongatus PCC7942 adapts different strategies to counteract on bromoxynil- and salt-mediated oxidative stress

“…The other modification revealed from proteome analysis was an up-regulation of bacterioferritin co-migratory protein-homologue peroxiredoxin-Q (PRX-Q) (Das and Bagchi 2011). Salinity and temperature are reported to enhance herbicide toxicity (DeLorenzo et al 2011). Consequently, herbicide resistance in a DCMU-resistant mutant of Prophyridium sp.…”

Combined effects of heatwaves and micropollutants on freshwater ecosystems: Towards an integrated assessment of extreme events in multiple stressors research

“…The authors found that a HW exposure (5 days, C: 25°C, H: 35°C) generally decreased the negative effects of the herbicides on the chlorophyll-a concentration, lipid content and starch content (Figure 5). However, opposite to Tasmin et al (2014), under simultaneous exposure to HW and herbicides, growth rate and cell density were generally decreased compared with the treatment containing only herbicides (Figure 5; Delorenzo et al, 2013).…”